Miniaturized liquid cooling device having droplet generator and pizeoelectric micropump

ABSTRACT

A miniaturized liquid cooling device ( 200 ) includes a heat absorber ( 20 ), a heat dissipater ( 30 ), a liquid driving device and a plurality of tubes ( 60 ) connecting the heat absorber, the heat dissipater and the liquid driving device together to form a loop. The liquid driving device includes a droplet generator ( 40 ) and a piezoelectric micro-pump ( 50 ). The droplet generator includes a plurality of control electrodes ( 422 ) and a reference electrode layer ( 442 ) corresponding to the control electrodes. A fluid channel ( 425 ) is formed between the control electrodes and the reference electrode layer. The piezoelectric micro-pump includes a piezoelectric block ( 518 ) and an oscillating diaphragm ( 517 ) capable of co-oscillating with the piezoelectric block for driving the working fluid to unidirectionally flow through a channel ( 513 ) defined in the piezoelectric micro-pump.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending U.S. patent application Ser. No. 11/836,734, filed on Aug. 9, 2007, and entitled “INK-JET HEAD AND PRINTER USING THE SAME”; and co-pending U.S. patent application Ser. No. 11/843,570, filed on Aug. 22, 2007, and entitled “MINIATURIZED LIQUID COOLING DEVICE”; and co-pending U.S. patent application entitled “MINIATURIZED LIQUID COOLING DEVICE” and filed on the same day as the instant application. The co-pending U.S. patent applications are assigned to the same assignee as the instant application. The disclosures of the above-identified applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to liquid cooling devices, and more particularly to a miniaturized liquid cooling device which has a droplet generator and a piezoelectric micro-pump.

2. Description of Related Art

Along with fast developments in electronic information industries, electronic components such as central processing units (CPUs) of computers are capable of operating at a much higher frequencies and speeds. As a result, the heat generated by the CPUs during normal operation is commensurately increased. If not quickly removed away from the CPUs this generated heat may cause them to become overheated and finally affect the workability and stability of the CPUs.

In order to remove the heat of the CPUs and hence keep the CPUs in normal working order, cooling devices must be provided to the CPUs to dissipate heat therefrom. Conventionally, extruded heat sinks combined with electric fans are frequently used for this heat dissipation purpose. These conventional cooling devices are sufficient for CPUs with low frequencies, but are unsatisfactory for cooling the current CPUs with high frequencies. Liquid cooling devices with high heat dissipation efficiencies are used for dissipating heat generated by high frequency CPUs.

The liquid cooling device includes a heat absorber absorbing heat from the CPU, a heat dissipater dissipating the heat to surrounding environment, a pump driving working fluid to circulate between the heat absorber and the heat dissipater, and a plurality of tubes connecting the heat absorber and the heat dissipater. The liquid cooling device satisfies the heat dissipation requirements of the high frequency CPU. However, the pump occupies a large volume, which increases the size of the liquid cooling device. This goes against the need for compact size in electronic products. Therefore, there is a need for a miniaturized liquid cooling device.

SUMMARY OF THE INVENTION

The present invention relates, in one aspect, to a miniaturized liquid cooling device. According to a preferred embodiment, the miniaturized liquid cooling device includes a heat absorber, a heat dissipater, a liquid driving device and a plurality of tubes connecting the heat absorber, the heat dissipater and the liquid driving device to form a loop. The liquid driving device includes a droplet generator and a piezoelectric micro-pump. The droplet generator includes a plurality of control electrodes and a reference electrode layer corresponding to the control electrodes. A fluid channel is formed between the control electrodes and the reference electrode layer. Voltages are regularly applied between the control electrodes and the reference electrode layer for dividing the working fluid into fluid droplets when the working fluid flows through the droplet generator. The piezoelectric micro-pump includes a piezoelectric block and an oscillating diaphragm capable of co-oscillating with the piezoelectric block for driving the working fluid to unidirectionally flow through a tiny channel defined in the piezoelectric micro-pump.

The present invention relates, in another aspect, to a liquid driving device used in the miniaturized liquid cooling device. According to a preferred embodiment, the liquid driving device includes a droplet generator and a piezoelectric micro-pump. The droplet generator includes a plurality of control electrodes and a reference electrode layer corresponding to the control electrodes. A fluid channel is formed between the control electrodes and the reference electrode layer. When voltages are regularly applied between the control electrodes and the reference electrode layer, the working fluid flowing through the droplet generator are divided into fluid droplets. The piezoelectric micro-pump connects with the droplet generator and are fluidically communicated with the droplet generator. The piezoelectric micro-pump includes a piezoelectric block and an oscillating diaphragm for co-oscillating with the piezoelectric block so as to drive the working fluid to flow through a tiny channel defined in the piezoelectric micro-pump.

Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an assembled view of a miniaturized liquid cooling device in accordance with a preferred embodiment of the present invention;

FIG. 2 is an exploded, isometric view of a droplet generator of the miniaturized liquid cooling device of FIG. 1;

FIG. 3 is an assembled view of the droplet generator of FIG. 2;

FIG. 4 is a part of a cut-away view of the droplet generator of FIG. 3, showing the part corresponding to a fluid channel of the droplet generator;

FIG. 5 is an exploded, isometric view of a piezoelectric micro-pump of the miniaturized liquid cooling device of FIG. 1;

FIG. 6 is an isometric, turned over view of a bottom plate of the piezoelectric micro-pump;

FIGS. 7A-7C are explanation views showing generation of a fluid droplet;

FIGS. 8A-8C are explanation views showing movement of the fluid droplet;

FIG. 9 is an exploded, isometric view of a liquid driving device of a miniaturized liquid cooling device in accordance with a second embodiment of the present invention, the liquid driving device including integrated droplet generator and piezoelectric micro-pump; and

FIGS. 10A-10B are explanation views showing a principle of an EWOD efficiency.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made to the drawing figures to describe the preferred embodiments in detail.

Referring to FIG. 1, a miniaturized liquid cooling device 200 according to a preferred embodiment of the present invention is shown. The liquid cooling device 200 includes a heat absorber 20, a heat dissipater 30, a miniaturized droplet generator 40, a piezoelectric micro-pump 50 and a plurality of tubes 60. The heat absorber 20, the heat dissipater 30, the droplet generator 40 and the piezoelectric micro-pump 50 are connected via the tubes 60 in such a way that a loop containing a working fluid is formed.

The heat absorber 20 thermally connects with a heat generating electronic component (not shown). The working fluid in the heat absorber 20 absorbs heat from the heat generating electronic component and is therefore heated. The droplet generator 40 and the piezoelectric micro-pump 50 cooperatively drive the heated working fluid to flow towards the heat dissipater 30. The heated working fluid is cooled at the heat dissipater 30 and driven to flow back to the heat absorber 20 through the droplet generator 40 and the piezoelectric micro-pump 50 to form a loop.

The heat absorber 20 is a rectangular shaped heat absorbing block. The heat absorber 20 includes a bottom base 22 defining a fluid passage (not shown) therein and a top cover 21 covering the bottom base 22. Inlet and outlet of the fluid passage of the bottom base 22 respectively connect with the piezoelectric micro-pump 50 and the heat dissipater 30 via the tubes 60.

The heat dissipater 30 is a heat sink including a base 31 and a plurality of fins 32 extending upwardly from the base 31. The base 31 of the heat dissipater 30 defines a fluid passage (not shown) therein. Inlet and outlet of the fluid passage of the base 31 respectively connect with the heat absorber 20 and the droplet generator 40 via the tubes 60. A plurality of heat dissipating posts may be arranged in the fluid passage of the heat dissipater 30 for increasing heat exchange efficiency between the heat dissipater 30 and the working fluid.

Referring to FIGS. 2 and 3, the droplet generator 40 includes a bottom electrode plate 42, a top electrode plate 44 hermetically covering the bottom electrode plate 42, a control circuit (not shown) electrically connecting the bottom electrode plate 42 with the top electrode plate 44, two elongated supporting members 46 sandwiched between the top electrode plate 44 and the bottom electrode plate 42, and first and second sealing blocks 48, 49 sealing two opposite ends of a fluid channel 425 formed between the top and the bottom electrode plates 44, 42 and the supporting members 46.

The bottom electrode plate 42 is rectangular shaped in profile and defines first and second openings 426, 427 at two opposite ends thereof. The first and the second sealing blocks 48, 49 are respectively received in the first and the second openings 426, 427, and seal the two opposite ends of the bottom electrode plate 42. The first and the second sealing blocks 48, 49 and the bottom electrode plate 42 respectively define mounting holes 482, 492, 432 therein, for fixing the first and the second sealing blocks 48, 49 to the bottom electrode plate 42. The first sealing block 48 defines an entrance 481 for the droplet generator 40, whilst the second sealing block 49 defines an exit 491 for the droplet generator 40. The entrance 481 of the droplet generator 40 has a round outer opening (not shown), a rectangular inner opening, and a fluid storage chamber (not shown) located between and communicating the outer opening with the inner opening. The exit 491 of the droplet generator 40 has a round outer opening, a rectangular inner opening (not shown) and a fluid storage chamber (not shown) located between and communicating the inner opening with the outer opening. A plurality of spaced control electrodes 422 are arranged on a top surface of the bottom electrode plate 42 along a longitudinal direction thereof. An elongated fluid slot 429 is defined at a middle portion of the bottom electrode plate 42 and extends along the longitudinal direction of the bottom electrode plate 42. A fluid storage pool 428 is defined between the leftmost control electrode 422 and the first opening 426 of the bottom electrode plate 42. The fluid storage pool 428 communicates the inner opening of the entrance 481 of the droplet generator 40 defined in the first sealing block 48 with a left end of the fluid slot 429, whilst a right end of the fluid slot 429 communicates with the inner opening of the exit 491 of the droplet generator 40 defined in the second sealing block 49. A width of the fluid slot 429 is so tiny that a capillary force can be generated which wicks the working fluid entering into the fluid slot 429.

The fluid slot 429 divides each of the control electrodes 422 into three parts, i.e. two parallel lateral parts 4221 at two opposite lateral sides of the fluid slot 429 and a middle part 4222 in the fluid slot 429. The control electrodes 422 respectively connect with a plurality of electric terminals 430 via a plurality connecting cords 431. The electric terminals 430 are positioned at two opposite lateral sides of the bottom electrode plate 42. Alternatively, the electric terminals 430 can merely be positioned at one lateral side of the bottom electrode plate 42. The supporting members 46 are respectively placed adjacent to the opposite lateral sides of the bottom electrode plate 42 via fasteners (not shown) extending through mounting holes 444, 461, 433 defined in the top electrode plate 44, the supporting members 46 and the bottom electrode plate 42. The fluid channel 425 is formed between a bottom surface of the top electrode plate 44, opposite inner surfaces of the supporting members 46 and the top surface of the bottom electrode plate 42, and has a width substantially equal to a width of each of the control electrodes 422. The electric terminals 430 are disposed outside the supporting members 46 so that the electric terminals 430 can connect with the control circuit.

Referring to FIG. 4, as viewed from the cut-away view, the bottom electrode plate 42 includes a substrate 421 made of glass. Alternatively, the substrate 421 can be made of silicone. The first and the second openings 426, 427, the fluid storage pool 428, the fluid slot 429 and the mounting holes 432, 433 are defined in the substrate 421 via mechanic manufacturing or wet etching method. A conductive and transparent ITO (indium tin oxide) glass layer is deposited on a top surface of the substrate 421 via chemical vapor deposition. The ITO glass layer is etched via photochemical etching so as to form the control electrodes 422, the connecting cords 431 and the electric terminals 430. A dielectric layer 423 made of silicone nitride (Si₃N₄) is deposited on top surfaces of the control electrodes 422, the connecting cords 431, and the electric terminals 430 via chemical vapor deposition method. A hydrophobic layer 424 made of Teflon is coated on the dielectric layer 423 via spin coating method, so that the working fluid cannot permeate to wet the control electrodes 422.

The top electrode plate 44 is rectangular shaped in profile and includes a substrate 441 made of glass. Alternatively, the substrate 441 can be made of silicone. The mounting holes 444 are defined in the substrate 441 via mechanical manufacturing or wet etching. A reference electrode layer 442 made of conductive and transparent ITO (indium tin oxide) glass is deposited on a bottom surface of the substrate 441 via chemical vapor deposition. A hydrophobic layer 443 made of Teflon is coated on the reference electrode layer 442 via spin coating method, so that the working fluid cannot permeate to wet the reference electrode layer 442. Alternatively, a dielectric layer made of silicone nitride (Si₃N₄) can be deposited between the reference electrode layer 442 and the hydrophobic layer 443 via chemical vapor deposition.

Referring to FIG. 5, the piezoelectric micro-pump 50 includes a rectangular bottom plate 51 and a rectangular top plate 52 hermetically covering the bottom plate 51. The bottom plate 51 defines a tiny channel 513 in a top surface 511 thereof. The tiny channel 513 extends through a longitudinal direction of the bottom plate 51 and includes a first section 514, a second section 516 and a third section 515. The first section 514 is located at a left side of the bottom plate 51, whilst the third section 515 is located at a right side of the bottom plate 51. The second section 516 is located between and communicates the first section 514 with the third section 515. The working fluid flows from the first section 514 through the second section 516 and towards the third section 515. A width of a cross-section of each of the first section 514, the second section 516 and the third section 515 gradually decreases from a left end towards a right end thereof. That is, the maximum width of each of the first section 514, the second section 516 and the third section 515 is formed at the left end thereof, and the minimum width of the first section 514, the second section 516 and the third section 515 is formed at the right end thereof. The maximum width of each of the cross section of the third section 515 is greater than that of the first section 514 but smaller than that of the second section 516. The minimum width of the cross section of the first section 514 is far smaller than the maximum width of the cross section of the second section 516. The minimum width of the cross section of the second section 516 is far smaller than the maximum width of the cross section of the third section 515. The width of the cross section of the tiny channel 513 is suddenly increased from the right end of the first section 514 towards the left end of the second section 516, and from the right end of the second section 516 towards the left end of the third section 515. That is, the width of the cross section of the tiny channel 513 is suddenly decreased from the left end of the second section 516 towards the right end of the first section 514, and from the left end of the third section 515 towards the right end of the second section 516. In this embodiment, the second section 516 of the tiny channel 513 has an isosceles triangular shaped cross section. Alternatively, the second section 516 may have other shaped cross sections whose width gradually decreases from the left end towards the right end thereof.

Referring to FIG. 6, a bottom surface 512 of the bottom plate 51 defines an isosceles triangular shaped indent 517 corresponding to the second section 516 of the tiny channel 513 of the top surface 511. An oscillating diaphragm 519 is formed between the second section 516 of the tiny channel 513 of the top surface 511 and the indent 517 of the bottom surface 512. A columned piezoelectric block 518 is attached to the oscillating diaphragm 519 and received in the indent 517 via PVD (physics vaporous deposit) method such as sputtering method, or PECVD (plasma enhanced chemical vapor deposit) method, or spin-coating method such as sol-gel method.

The piezoelectric block 518 electrically connects with the control circuit. Electric signals sending from the control circuit cause the piezoelectric block 518 to distort, which induces the oscillating diaphragm 519 to upwardly and downwardly co-oscillate with the piezoelectric block 518. If the piezoelectric block 518 and the oscillating diaphragm 519 distort downwardly, a volume of the second section 516 of the tiny channel 513 is increased, thereby inducing the working fluid in the first section 514 and the third section 515 to flow towards the second section 516. Since there is a sudden increase of the cross sectional area from the right end of the first section 514 towards the left end of the second section 516, and a sudden decrease of the cross sectional area from the left end of the third section 515 towards the right end of the second section 516, a flux of the working fluid from the first section 514 towards the second section 516 is far more than a flux of the working fluid from the third section 515 towards the second section 516. There is more working fluid entering into the tiny channel 513 of the piezoelectric micro-pump 50. That is, the working fluid flows from the left side of the tiny channel 513 towards the right side thereof. If the piezoelectric block 518 and the oscillating diaphragm 519 distort upwardly, a volume of the second section 516 of the tiny channel 513 is decreased, which induces the working fluid in the second section 516 to flow towards the first section 514 and the third section 515. Since there is a sudden decrease of the cross sectional area from the left end of the second section 516 towards the right end of the first section 514, and a sudden increase of the cross sectional area from the right end of the second section 516 towards the left end of the third section 515, a flux of the working fluid from the second section 516 towards the first section 514 is far less than a flux of the working fluid from the second section 516 towards the third section 515. There is more working fluid flowing out of the tiny channel 513 of the piezoelectric micro-pump 50. That is, the working fluid flows from the left side of the tiny channel 513 towards the right side thereof. Therefore, during the oscillation of the oscillating diaphragm 519 and the piezoelectric block 518, the working fluid continuously enters into and flows out of the piezoelectric micro-pump 50.

Referring to FIGS. 7A to 7C, during operation of the droplet generator 40, a fluid segment B of the working fluid contained in the fluid storage pool 428 is wicked into the left end of the fluid slot 429 and the leftmost control electrode 422 a. A voltage is applied to the control electrode 422 a by the control circuit. Therefore, the surface tension of a front side (right side) of the fluid segment B varies due to EWOD (electrowetting-on-dielectric) effect. Referring to FIGS. 10A and 10B, the EWOD effect is a phenomenon where a contact angle of a front or a rear side of a fluid segment or a fluid droplet varies when a voltage is applied on the front or the rear side of the fluid droplet, whilst a contact angle of the other side of the fluid segment/the fluid droplet remains as before. Therefore, the contact angles of the front and rear sides of the fluid segment/the fluid droplet are different from each other, which causes a difference between surface tensions of the front and rear sides of the fluid droplet/fluid segment to be generated. The difference between the surface tensions drives the fluid segment to move towards a place having higher voltage. That is, the fluid segment B moves from the fluid storage pool 428 towards the fluid channel 425 corresponding to the control electrode 422 a. When a front of the fluid segment B moves to the next control electrode 422 b, a voltage from the control circuit is applied to the control electrode 422 b. The fluid segment B moves along the fluid channel 425 from the control electrode 422 a towards the control electrode 422 b. When the front of the fluid segment B moves to the further next control electrode 422 c, a voltage from the control circuit is applied to the control electrode 422 c and the voltage applied to the control electrode 422 b is cut off. At this time, the front of the fluid segment B is driven to move along the fluid channel 425 towards the control electrode 422 c, whilst a rear (left side) of the fluid segment B is driven to move towards the control electrode 422 a. The fluid segment B is cut into two parts and a fluid droplet D is generated at the control electrode 422 c.

Referring to FIGS. 8A to 8C, the fluid droplet D continues to move towards the control electrode 422 d. When a front of the fluid droplet D moves to the control electrode 422 d, a voltage from the control circuit is applied to the control electrode 422 d and the voltage applied to the control electrode 422 c is cut off. The fluid droplet D is driven to move towards the control electrode 422 d. When the front of the fluid droplet D moves to the control electrode 422 e, a voltage from the control circuit is applied to the control electrode 422 e and the voltage applied to the control electrode 422 d is cut off. The fluid droplet D continues to move towards the control electrode 422 e. The voltage is regularly applied to the control electrodes 422 d, 422 e, 422 f, etc. and regularly cut off from the control electrodes 422 c, 422 d, 422 e, etc. in that order. The fluid droplet D is driven to move towards the right end of the fluid channel 425 and enters into the inner opening of the exit 491 of the droplet generator 40 defined in the second sealing block 49. Hereinabove description only shows a movement of one fluid droplet D. Actually, there are many more fluid droplets D moving at the same time, and there are many more fluid droplets D continuously entering into the second sealing block 49. When there is enough working fluid in the second sealing block 49, the working fluid is pressed out of the second sealing block 49 and moves towards the piezoelectric micro-pump 50. The working fluid is accelerated in the piezoelectric micro-pump 50 and flows towards the heat absorber 20 to absorb heat from the heat generating electronic component. The working fluid is then driven into the heat dissipater 30 and releases the heat to surrounding environment. Then, the working fluid returns to the droplet generator 40 and circulates in the liquid cooling device 200 to continuously absorb heat from the heat absorber 20 and dissipate the heat to the surrounding environment via the heat dissipater 30. Therefore, the heat generated from the heat generating electronic component is dissipated.

In the present liquid cooling device 200, the droplet generator 40 and the piezoelectric micro-pump 50 cooperatively form a liquid driving device for the liquid cooling device 200, so as to strengthen the power for driving the working fluid to circulate in the liquid cooling device 200 and increase heat dissipation efficiency of the liquid cooling device 200. The droplet generator 40 and the piezoelectric micro-pump 50 occupy small sizes, which decreases the size of the entire liquid cooling device 200 in such a way that the liquid cooling device 200 can be used in compact electronic products such as laptop computers. The droplet generator 40 drives the working fluid circulating in the liquid cooling device 200 via continuously generating fluid droplets D under EWOD efficiency. There is no noise generated during the operation of the liquid cooing device 200. Therefore, a quiet working environment is obtained. The piezoelectric micro-pump 50 drives the working fluid to unidirectionally circulate in the liquid cooling device 200. There is no need to add a check valve in the piezoelectric micro-pump 50 to prevent the working fluid from flowing backward and thereby noise generated by the check valve is eliminated.

In the present liquid cooling device 200, the first and the second sealing blocks 48, 49, and the supporting members 46 are separately formed with the bottom electrode plate 42 and the top electrode plate 44. Alternatively, the first and the second sealing blocks 48, 49, and the supporting members 46 can be integrally formed with the bottom electrode plate 42 or the top electrode plate 44 from a single piece. If the first and the second sealing blocks 48, 49 are integrally formed with the bottom electrode plate 42, there is no need to define the first and the second openings 426, 427 in the bottom electrode plate 42. In the present liquid cooling device 200, the droplet generator 40 has the liquid storage pool 428 disposed between the first sealing block 48 and the fluid slot 429. Alternatively, the liquid storage pool 428 can be omitted, which allows the entrance 481 of the droplet generator 40 defined in the first sealing block 48 to directly communicate with the left end of the fluid channel 425. In the present liquid cooling device 200, the working fluid enters into and pours out of the droplet generator 40 via the entrance 481 and the exit 491 respectively defined in the first sealing block 48 and the second sealing block 49. Alternatively, the entrance and the exit 481, 491 in the first and the second sealing blocks 48, 49 can be omitted. In that situation, the working fluid can enter into and pour out of the droplet generator 40 via entrance and exit defined in the top electrode plate 44. In the present liquid cooling device 200, the top electrode plate 44 is supported on the bottom electrode plate 42 via the supporting members 46. Alternatively, the supporting members 46 can be omitted. In that situation, the top electrode plate 44 directly and hermetically contacts with the bottom electrode plate 42. The fluid channel 425 is defined in the bottom electrode plate 42 and has a width substantially equal to or a bit greater than that of the control electrode 422.

Referring to FIG. 9, a second embodiment of the present liquid cooling device is shown. In this embodiment, the droplet generator and the piezoelectric micro-pump is integrated between a bottom plate 71 and a top plate 72. The liquid storage pool of the droplet generator is omitted. The fluid channel 716 of the droplet generator and the tiny channel 712 of the piezoelectric micro-pump are defined in the bottom plate 71. The fluid channel 716 of the droplet generator is arranged at a left side of and communicates with the tiny channel 712 of the piezoelectric micro-pump. A plurality of control electrodes 711 is positioned in the fluid channel 716 of the droplet generator. The top plate 72 has a reference electrode layer (not shown) above the control electrodes 711. The reference electrode layer and the control electrodes 711 are electrically connected via the control circuit. The tiny channel 712 of the piezoelectric micro-pump includes a first section 713, a second section 715 and a third section 714. The first section 713 communicates the second section 715 with the fluid channel 716 of the droplet generator. The second section 715 communicates the first section 713 with the third section 714. The working fluid flows from the fluid channel 716 of the droplet generator towards the third section 714 of the tiny channel 712 of the piezoelectric micro-pump. The integrated droplet generator and the piezoelectric micro-pump further decreases size of the liquid cooling device. There are no tubes connected between the droplet generator and the piezoelectric micro-pump in the second embodiment, which also simplifies the assembly of the liquid cooling device.

It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A liquid driving device comprising: a droplet generator comprising a plurality of control electrodes and a reference electrode layer corresponding to the control electrodes, a fluid channel being formed between the control electrodes and the reference electrode layer, when voltages being regularly applied between the control electrodes and the reference electrode layer, the working fluid flowing through the droplet generator is divided into fluid droplets; and a piezoelectric micro-pump connected with the droplet generator and fluidically communicated with the droplet generator, the piezoelectric micro-pump comprising a piezoelectric block and an oscillating diaphragm for co-oscillating with the piezoelectric block so as to drive the working fluid to flow through a channel defined in the piezoelectric micro-pump.
 2. The liquid driving device as described in claim 1, wherein the piezoelectric micro-pump includes a first plate and a second plate covering the first plate, the channel being defined in a first surface of the first plate and comprising a first section, a second section and a third section, the second section communicating the first section with the third section, an indent being defined in an opposite second surface of the first plate, the oscillating diaphragm being formed between the second section of the channel of the first surface and the indent of the second surface, the piezoelectric block being attached to the diaphragm and received in the indent of the second surface.
 3. The liquid driving device as described in claim 2, wherein the working fluid flows from the first section towards the third section, and a width of a cross section of each of the first section, the second section and the third section gradually decreases along a flow direction of the working fluid.
 4. The liquid driving device as described in claim 3, wherein a maximum width of the cross section of the third section is greater than that of the first section but smaller than that of the second section.
 5. The liquid driving device as described in claim 3, wherein a minimum width of the cross section of the first section is smaller than a maximum width of the cross section of the second section, and a minimum width of the cross section of the second section is smaller than a maximum width of the cross section of the third section.
 6. The liquid driving device as described in claim 1, wherein the droplet generator comprises a first electrode plate and a second electrode plate covering the first electrode plate, the control electrodes and the reference electrode layer being respectively formed on the first and the second electrode plates, the fluid channel being defined between the first and the second electrode plates, the droplet generator further comprising two sealing blocks hermetically disposed at two opposite ends of the fluid channel, two openings of the droplet generator being respectively defined in the sealing blocks functioning as entrance and exit for the working fluid.
 7. The liquid driving device as described in claim 6, wherein the droplet generator comprises two supporting members disposed at two opposite sides of the fluid channel and hermetically supporting the second electrode plate on the first electrode plate.
 8. The liquid driving device as described in claim 1, wherein the droplet generator and the piezoelectric micro-pump are integrally formed from a first plate and a second plate covering the first plate, the fluid channel of the droplet generator and the channel of the piezoelectric micro-pump are defined in a first surface of the first plate and communicate with each other.
 9. The liquid driving device as described in claim 8, wherein the control electrodes are disposed in the fluid channel and the reference electrode layer is formed on the second plate, the channel of the piezoelectric micro-pump comprising a first section, a second section and a third section, the first section communicating the fluid channel with the second section, the second section communicating the first section with the third section.
 10. The liquid driving device as described in claim 9, wherein the first plate defines an indent in an opposite second surface thereof, the oscillating diaphragm being formed between the second section of the channel of the first surface and the indent of the second surface, the piezoelectric block being attached to the diaphragm and received in the indent of the second surface.
 11. A miniaturized liquid cooling device comprising: a heat absorber; a heat dissipater; a liquid driving device comprising: a droplet generator comprising a plurality of control electrodes and a reference electrode layer corresponding to the control electrodes, a fluid channel being formed between the control electrodes and the reference electrode layer, voltages being regularly applied between the control electrodes and the reference electrode layer adapted for dividing the working fluid into fluid droplets when the working fluid flows through the droplet generator; and a piezoelectric micro-pump comprising a piezoelectric block and an oscillating diaphragm capable of co-oscillating with the piezoelectric block adapted for driving the working fluid to unidirectionally flow through a channel defined in the piezoelectric micro-pump; and a plurality of tubes connecting the heat absorber, the heat dissipater, the droplet generator and the piezoelectric micro-pump together to form a loop.
 12. The miniaturized liquid cooling device as described in claim 11, wherein the piezoelectric micro-pump includes a first plate and a second plate covering the first plate, the channel being defined in a first surface of the first plate and comprising a first section, a second section and a third section, the second section communicating the first section with the third section, an indent being defined in an opposite second surface of the first plate, the oscillating diaphragm being formed between the second section of the channel of the first surface and the indent of the second surface, the piezoelectric block being attached to the diaphragm and received in the indent of the second surface.
 13. The miniaturized liquid cooling device as described in claim 12, wherein the working fluid flows from the first section towards the third section, and a width of a cross section of each of the first section, the second section and the third section gradually decreases along a flow direction of the working fluid.
 14. The miniaturized liquid cooling device as described in claim 13, wherein a maximum width of the cross section of the third section is greater than that of the first section but smaller than that of the second section.
 15. The miniaturized liquid cooling device as described in claim 13, wherein a minimum width of the cross section of the first section is smaller than a maximum width of the cross section of the second section, and a minimum width of the cross section of the second section is smaller than a maximum width of the cross section of the third section.
 16. The miniaturized liquid cooling device as described in claim 11, wherein the droplet generator and the piezoelectric micro-pump are integrally formed from a first plate and a second plate covering the first plate, the fluid channel of the droplet generator and the channel of the piezoelectric micro-pump are defined in a first surface of the first plate and communicate with each other.
 17. The miniaturized liquid cooling device as described in claim 16, wherein the control electrodes of the droplet generator are disposed in the fluid channel and the reference electrode layer of the droplet generator is formed on the second plate, the channel of the piezoelectric micro-pump comprising a first section, a second section and a third section, the first section communicating the fluid channel with the second section, the second section communicating the first section with the third section.
 18. The miniaturized liquid cooling device as described in claim 17, wherein the first plate defines an indent in an opposite second surface thereof, the oscillating diaphragm being formed between the second section of the channel of the first surface and the indent of the second surface, the piezoelectric block being attached to the diaphragm and received in the indent of the second surface. 